package org.ruanjj;


import java.net.http.HttpClient;
import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello world!");
        AtomicInteger atomicInteger = new AtomicInteger();
        atomicInteger.getAndIncrement();

        List<String> list = Arrays.asList(new String[]{"A","B","C"});
        System.out.println(list);
        Iterator<String> iterator = list.iterator();
        while(iterator.hasNext()) {
            System.out.println(iterator.next());
        }

        Queue a = new LinkedList();
        Stack b = new Stack();
        Deque d = new LinkedList();

        int[] nums = new int[]{1,2,3,4,5};

        nums = new int[nums.length+1];
        nums[0] = 0;
        System.out.println(nums);

        List<Integer> t = new ArrayList<>(List.of(0, 1, 2, 3));
        Collections.swap(t,2,0);
        String s = "1 + 1";
        char[] c = s.toCharArray();
        System.out.println(Character.isDigit('1'));
        System.out.println(s.substring(0, 1));
        Scanner scan = new Scanner(System.in);
        System.out.println('z' - 'a');
    }
}